Light transmitting building material and method for producing the same

ABSTRACT

A light-transmitting structure for use as a building block or panel, and a related method of fabrication. The structure includes a composite of a primary building material and one or more light-transmitting elements. The primary building material may have structural and/or insulative characteristics. The light-transmitting elements extend from one surface of the primary building material to the other and preferably make up a small part of the bulk of the structure. One or more light-concentrating elements are positioned on one or both surfaces of the structure and are configured to concentrate incoming light rays to the light-transmitting elements. The light-transmitting elements may be optical fibers, optical film in a parallel or intersecting arrangements, or other suitable geometries. The light-concentrating elements may be spherical, aspherical, or other geometries suitable for enabling light transmission through the primary building material via the light-transmitting elements. The structure may be fabricated in a variety of ways. In one process, the light-transmitting and light-concentrating elements may be formed separately and joined together in an aligned manner. In another process, both elements may be formed at the same time, either using a preformed mold, extrusion or shaping and selectively curing portions of a fluid with optical characteristics. The panel may be used to introduce light and or heating sunshine through the structure with little impact on its structural and/or insulative characteristics.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to building structures. More particularly,the present invention relates to traditionally opaque building materialsincluding, but not limited to, cement, concrete blocks, wood, fiberbatting and solid, cellular and porous polymeric structural and covermaterials. Still more particularly, the present invention relates tosystems and methods for making such traditional building materialscapable of light transmission.

2. Description of the Prior Art

Buildings within which people live, work and play must have certainphysical characteristics to ensure structural integrity in a manner thatpreserves the condition of the building and the security and comfort ofthe people within. That is, buildings are built to remain in place forsome period of time, and to be used as intended, under the particularenvironmental conditions to be expected where the building is located.Unfortunately, these desired characteristics of a building tend toproduce a conflict in the selection of materials used to build thebuilding.

The primary conflict in building material selection relates to the useof materials that can be divided into two general categories: opaque andlight transmitting. Opaque materials are those that provide structuralintegrity and protection from the external environment. Opaque materialsmost commonly used to fabricate buildings include cement, concreteblocks, wood, fiber glass insulation and solid, cellular and porouspolymeric structural and cover materials. Light transmitting materials,on the other hand, provide the building occupants with day lighting andoptionally the ability to observe the environment beyond the buildingwithout direct exposure thereto. Light transmitting materials mostcommonly used in the fabrication of at least portions of a building,primarily the windows, include glass and polymeric materials.

The limitations associated with each type of material are as fundamentalas their advantages. Building occupants cannot see through the opaquestructural materials to the outside environment. The opaque materials donot let in sunlight. As a result, sunlight cannot heat the interior ofthe building and artificial lighting is required to light the interiorof the building. On the other hand, a window does not have theinsulative or structural characteristics associated with opaquematerials. As a result, building heat loss tends to occur through itswindows much more so than through its opaque walls.

Some attempts have been made or disclosed to address the limitationsassociated with opaque building materials. Published US patentapplication Pub. No. 2005/0183372 and PCT application no. WO 03/097954describe a building block with light-transmitting fibers, apparentlysold under the trade name Litracon™ offered by the Litracon Company ofHungary. The Litracon™ product is fabricated in blocks that may beplaced together. The visual image is blurry through the blocks and lighttransmission appears to be diffuse when the sample shown on thecompany's website is viewed. This is due to the optical fibers' propertyof transmitting light entering from many angles causing mixing andblurring of all but the closest objects or shadows. Also, the opticalfibers provide for some light transmission but the light transmission islimited to the percentage of optical fiber included in the material.This creates a large trade off between light transmission andmaintenance of the physical properties of the building material. U.S.Pat. No. 4,796,404 describes a light-transmitting thermal barrier. Thelight is also diffused in this structure. Further, the structurerequires a trade-off between thickness, which determines thermalinsulation characteristics, and light transmission. Finally, the CabotCorporation offers an aerogel powder used to fill the core of lightingpanels to enhance thermal insulation. However, the powder scatters lightsuch that the panel may not be used as a window and, again, there is atrade off between light transmission and thermal insulationcharacteristics. Also, none of the above solutions provide for theselective transmission of light based on incoming angle which can allowfor heat gain in a building during the winter months while rejectingbuilding heating light during the summer months, for example.

Therefore, what is needed is a building material having structuraland/or insulative characteristics of interest in the fabrication ofcommercial and residential buildings while providing such a materialwith optimized light-transmitting characteristics. Also, what is neededis such a building material wherein light passing therethrough may befocused rather than diffused. Further, what is needed is such alight-transmitting material that enables relatively clear viewing frominside the building of features outside of the building. Still furtherneeded is a building material that can selectively transmit a majorityof sunlight during the heating season while limiting light transmissionduring the non-heating season.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide building materialshaving structural and/or insulative characteristics of interest in thefabrication of commercial and residential buildings, and further havinglight-transmitting characteristics. It is also an object of the presentinvention to provide such a building material that transmits a largepercentage of the light striking the panel's outer surface, thepercentage being largely independent of the panel's thickness. In onepreferred embodiment the panel transmits most of the light striking theouter surface during winter months while rejecting most of the lightduring the summer months. It is a further object of the presentinvention to optionally provide such a light-transmitting material thatenables relatively clear viewing from inside the building of featuresoutside of the building. In this embodiment the angles of lighttransmitted are tightly controlled such that image transmission ispossible.

These and other objects are achieved by the present invention, which isa combination of components including a primary structural and/orinsulative material, one or more light-transmitting elements, and one ormore light-concentrating elements. The invention is a building block orpanel of selectable thickness formed primarily of the structural and/orinsulative material. The structural material may be, for example,concrete. The insulative material may be, for example a polymeric foam.This insulative and/or structural material will henceforth be referredto as the primary building material. The light-transmitting element(s)extend completely through the thickness of the panel, from the panel'sfirst lateral surface to its second lateral surface. The primarybuilding material occupies all or substantially all of the space betweenthe faces of the panel not otherwise occupied by the light-transmittingelements. The light-transmitting elements are optically transparentmaterials, preferably formed of glass or polymeric material. It isintended that the light-transmitting elements make up a relatively smallportion of the overall cross-section of the panel. Thelight-concentrating elements are attached to one or both of the firstand second lateral surfaces of the panel. They are configured andarranged such that a majority of light (either from a single angle ormultiple angles) striking the lateral surface of the panel isconcentrated into the light-transmitting elements. As a result, amajority of the light striking the panel made of substantially opaquebuilding material passes through the light-transmitting elements fromthe one lateral surface through to the other. A substantial amount oflight is transmitted into the interior of the building using a minimalamount of light-transmitting elements, thereby maximizing the amount ofstructural and/or insulative material of the panel.

In one embodiment of the invention, the light-concentrating elementsconcentrate light striking the first side of the panel oriented to facethe exterior of the building from a selectable specific angle or set ofangles such that the light transmitted from the second orinterior-facing surface of the panel forms an image, as would be thecase with a window. In a second embodiment of the invention, thelight-concentrating elements concentrate light from the exterior throughthe light-transmitting elements from as wide a set of entrance angles aspossible such that the panel transmits a maximum percentage of lightacross the interior-facing surface to the interior of the building tomaximize lighting and/or heating within the building. In a thirdembodiment, the light-transmitting elements are shaped to allow lightfrom the light-concentrating elements to enter them only from certainangles of the sun so as to selectively allow sunlight to cross the panelwhen desired, such as only during specific hours of the day or specificdays of the year. Additionally, one or more methods of fabricating thepanels of the present invention, including the use of commerciallyavailable materials and existing general fabrication techniques, aredescribed herein.

These and other advantages and aspects of the panel and related methodof fabrication of the present invention will become apparent upon reviewof the following detailed description, the accompanying drawings, andthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of the light-transmitting panel ofthe present invention showing the interior-facing side of the panel tothe left and the exterior-facing side of the panel with array oflight-concentrating elements to the right.

FIG. 2 is a front view of the exterior-facing side of the panel of thepresent invention showing one embodiment of an array oflight-concentrating elements.

FIG. 3 is a cross-sectional side view showing an individuallight-concentrating element concentrating light through alight-transmitting element with the interior-facing side of the panel ofthe present invention to the left and the exterior-facing side of thepanel to the right.

FIG. 4 is a front elevation view of a spherical lens as alight-concentrating element.

FIG. 5 is a cross-sectional side view of a set of cylindrical lenses asthe light-concentrating elements.

FIG. 6 is a front elevation view of a panel of the present inventionshowing the light-transmitting elements as an array of fibers.

FIG. 7 is a front elevation view of a panel of the present inventionshowing the light-transmitting elements as a parallel array of opticalfilms.

FIG. 8 is a front elevation view of a panel of the present inventionshowing the light-transmitting elements as a grid array of opticalfilms.

FIG. 9 is a front elevation view of a close-packed array of sphericallenses showing the location of curved light guides arranged fortransmitting sunlight through most of the day during winter months whilerejecting most of the sunlight during summer months.

FIG. 10 is a cross-sectional side view of the close-packed array ofspherical lenses of FIG. 9, showing a close-up of two lenses withassociated light-transmitting elements.

FIG. 11 is a sun chart used for calculating the sun's path for thelatitude coordinate indicated to enable selection of the positioning ofthe light-transmitting elements of the embodiment of the invention ofFIGS. 9 and 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A building panel 10 of the present invention is shown in FIG. 1. Thepanel 10 includes a first surface 14 that will be referred to herein asan exterior-facing panel side 14 or simply exterior side 14. The panel10 further includes a second surface 12 that will be referred to hereinas an interior-facing panel side 12 or simply interior side 12. Thepanel is preferably fabricated with a uniform selectable thicknessextending from the exterior side 14 to the interior side 12, although itis contemplated that the thickness may be varied if desired (as when theoutside surface is made to resemble a house's siding). The panel 10 iseffectively a three-dimensional structure having selectable dimensionsestablishing the area it covers. The coverage area may be rectangular,circular or other shape and the panel may be framed or not forinstallation. The interior side 12 and the exterior side 14 are referredto as such to provide proper orientation of the components of the panel10 when the panel forms part of a building structure. Specifically, theinterior side 12 is that side of the panel 10 which faces toward theinterior of the building, while the exterior side 14 is that side of thepanel 10, which faces the environment surrounding the building, of whichthe panel 10 forms a part.

With continuing reference to FIG. 1 and reference to FIG. 2, the panel10 is fabricated of a combination of components, including a primarybuilding material 16, one or more light-transmitting elements 18, andone or more light-concentrating elements 20. The primary buildingmaterial 16 provides the structural integrity and/or any thermalinsulation characteristics of the panel 10. It is to be noted that theprimary building material 16 may be a primarily insulative material,with structural support provided to the panel 10 by some additionalmeans. For example, both the interior side 12 and the exterior side 14of the panel 10 may be formed of continuous sheets of transparentpolymer, which are held together by the light transmitting-elements 18to form a strong panel, even when the primary building material 16 is anon-structural material such as fiberglass insulation, or an insulativepowder such as aerogel powder or perlite. The light-transmittingelements 18 extend completely through the thickness of the panel betweenthe interior side 12 and the exterior side 14. The light-concentratingelements 20 are positioned on the exterior side 14 of the panel 10.However, it is contemplated that the present invention may be formedwith the light-concentrating elements 20 on the interior side 12 insteadof the exterior side 14, or on both the interior side 12 and theexterior side 14. The location of the light-concentrating elements 20 isdependent upon the particular light and/or heat transmissioncharacteristics of interest for the panel 10.

The arrangement of the panel 10 of the present invention providesimproved energy consumption characteristics of the building of which itforms a part. As previously noted, windows generally have lowerinsulative or R-value characteristics than walls and insulativematerials. Windows therefore lose heat at a faster rate than do thewalls when the exterior of the building is colder than the interior.However, the panel 10 effectively acts as a window in that it isconfigured to allow light transmission. It also has insulativecharacteristics approaching those of insulated walls and, in fact, maybe a net heat gain as light permitted to pass therethrough can be usedas a heat source at the building's interior. The panel 10 may beconfigured to transfer light from a specified entry angle (or angles)and concentrate it through the light-concentrating elements 20 to thelight-transmitting elements 18 to produce on the interior side 12 of thepanel 10 a discernible image representative of the image in existence atthe exterior side 14 of the panel 10. That may be achieved by usinglens-like optical geometries as the light-concentrating elements 20 onthe exterior side 14 of the panel 10. Alternatively, the panel 10 may beconfigured to collect light from the outside of the building at multipleangles in order to maximize light and/or heat transfer, without regardto image quality. That may be achieved by using nonimaging opticalgeometries as the light-concentrating elements 20 on the exterior side14 of the panel 10. It may also be achieved by using spherical lensarrays coupled to light guides that are curved such that as the sun'sangle changes in the sky the light focused to the back side of the lenscontinues to enter the light guide as will be described herein withrespect to FIGS. 9-11. As an example, the panel 10 may be used as askylight or wall panel, configured to produce either or both ofdiscernible images (without the inherent heat loss associated withconventional windows and skylights) and light/heat transfer improvement.

An effective aspect of the panel 10 of the present invention is thearrangement of the light-transmitting elements 18 with respect to theprimary building material 16 for both imaging and light/heat transferimprovement. Specifically, each of the light-transmitting elements 18,which elements are preferably some form of light-transmitting fibers,are combined with the primary building material 16 such that they form asmall percentage of the total volume of the panel 10. In that way, thestructural and/or insulative characteristics of the panel 10 approachthat of the particular material used as the primary building material16. The addition of the light-concentrating elements 20 on the surfaceonly of the panel 10 provides a far greater light-impacting surface thanthe ends of the individual fibers that are the light-transmittingelements 18, but without effect on the structural and insulativecharacteristics of the panel 10 as established primarily by thecharacteristics of the primary building material 16. That light hittingthe light-concentrating elements 20 is then substantially captured, theextent of that capturing being dependent upon the number, type andlocation of the individual light-transmitting elements 18 and thelight-concentrating elements 20.

One example of the panel 10 as an insulative panel appearing to betransparent at least from within the building includes an array oflenses as the light-concentrating elements 20 positioned on the exteriorside 14 of the panel 10, each lens having a diameter about 10 timeslarger than the diameter of the individual fibers that are thelight-transmitting elements 18. In this arrangement, there would be aone-to-one correspondence of lens to fiber. In that arrangement, thecross-sectional area of the fiber is only about 1/100 of thecross-sectional area of the lens. By close packing the lenses to coversubstantially the entire exterior side 14 of the panel 10, the fiberswould only consume about one percent of the total volume of the panel10, leaving the remaining 99% of the panel 10 to be formed of theprimary building material 16. As a result, the panel 10 is substantiallythe primary building material 16, for structural and/or insulativepurposes, while at the same time most all of the light contacting theexterior side 1.4 of the panel 10 from a set of angles is transmittingthrough to the interior side 12 of the panel. If used primarily forinsulative purposes, the panel 10 would have an R-value nearly the sameas that of conventional insulative building materials, but withoutappearing to be opaque to the individual at the interior side 12 of thepanel 10. The quality of the image observed by that individual isdependent upon the lens size selected, the observed image formed ofpixels corresponding in size to the size of the lenses positioned on theexterior side 14 of the panel 10.

The application of the light-concentrating elements 20 to the exteriorside 14 of the panel 10 resolves the problem associated with existingattempts to render structural and/or insulative materials transparent,at least to an extent. Specifically, the light-concentrating elements 20enable a much higher light transmission capability than possible withthe light-transmitting elements 18 alone. As an example, a buildingproduct formed substantially of structural or insulative material withone percent of light-transmitting fibers extending from one surface tothe other will only transmit to one surface something less than onepercent of the light contacting the other surface, assuming normallosses such as from surface reflection. If more light transmission is ofinterest, more light-transmitting fibers must be incorporated. However,if there is an interest in transmitting a substantial portion of thelight, then a corresponding proportion of the building product wouldhave to include the light-transmitting fibers, with a correspondingreduction in the amount of structural/insulative material making up thebuilding product and related reduction in structural/insulativecharacteristics.

FIG. 3 provides a close-up view of the concentrating or focusing oflight into an exemplar one of the light-transmitting elements 18 by anexemplar one of the light-concentrating elements 20. Initial light rays22 contacting the light-concentrating element 20 from a source externalto the building of which the panel 10 forms a part are focused into thelight-transmitting element 18. Dependent upon the particular materialselected to form the light-transmitting element 18, a substantialportion of concentrating light rays 24 pass therethrough and emerge atthe interior side 12 of the panel 10 as a transmitted light raycomposition 26 producing an image pixel corresponding in size to thesize of the light-concentrating element 20. The size, shape, materialselected and proximity of the light-concentrating element 20 determinesthe focal point 28 of the focused initial rays 22 and the percentage oflight passing to the light-transmitting element 18.

Those skilled in the art will recognize the types of materials andshapes to select for the fabrication of the light-concentrating elements20, and their placement with respect to the location of thelight-transmitting elements 18 on the exterior side 14 of the panel 20.For example, one shape of the light-concentrating element 20 may bespherical, as shown in FIG. 4, or it may be cylindrical, as shown inFIG. 5. If formed as spheres, the light-concentrating element 20 may beused to focus the initial light rays 22 to a point, suitable forlight-transmitting elements 18 that are individual fibers of circularcross-section. Alternatively the fibers can possess any cross-sectionalshape such as those with an arch-like geometry to capture the sun's archlike track through the sky as the focused light forms a point that movesin an arch across the back surface of the corresponding lens element. Ifformed cylindrically, the light-concentrating element 20 may be used tofocus the initial light rays 22 into a line rather than a point,suitable for light-transmitting elements 20 that are in a form otherthan individual fibers. The use of multiple optical elements directinglight into a single light-transmitting element is also envisioned to aidin the formation of crisp images.

In the example embodiment of the panel 10 of the present invention asdescribed above, the light-transmitting elements 18 have been describedas light-transmitting fibers arranged within the primary buildingmaterial 16. An example representation of the arrangement of suchlight-transmitting fibers, identified individually as fibers 30, isshown in FIG. 6. It can be seen that the example configuration includesthe fibers 30 in an evenly spaced square pattern within the primarybuilding material 16. Alternatively, the fibers 30 may be positionedwithin the primary building material 16 in a close-packed pattern or arandomized pattern, dependent upon the particular light-transmittingcharacteristic of interest. The number and size of the fibers 30 arealso selectable as a function of the particular light-transmittingcharacteristic of interest. The fibers 30 may be used in combinationwith the light-concentrating elements 20 shaped as represented in FIG.4.

A first alternative embodiment of the configuration of thelight-transmitting elements 18 of the panel 10 of the present inventionis shown in FIG. 7. In that configuration, the light-transmittingelements, identified as sheets 32, are formed planar films oflight-transmitting material positioned in a uniform spacing through thethickness of the panel 10 and retained in position by the primarybuilding material 16. The panel 10 is formed as a lamination of theprimary building material 16 preferably alternating with the sheets 32.The sheets 32 may be uniformly spaced, as shown, or they may bestaggered in alternative or randomized patterns, dependent upon thelight-transmitting characteristic of interest. Additionally, one or moreof the individual light-transmitting sheets 32 may be formed of uniformthickness from the exterior side 14 to the interior side 12 of the panel10. Alternatively, the sheets 32 may be of varied thickness, with thesheet thickness substantially uniform through the primary buildingmaterial 16, but having either or both ends thereof at the exterior side14 and/or the interior side 12 of greater thickness. This alternativethickness arrangement allows for greater light-receiving orlight-producing capability where the light enters or exits the sheets32, but without increasing the overall volume of the light-transmittingelements within the primary building material 16. As a result, thisparticular arrangement aids in maintaining the structural and/orinsulative characteristics of the panel 10 while enhancing lighttransmission. The sheets 32 may be used in combination with thelight-concentrating elements 20 shaped as represented in FIG. 5.

A second alternative embodiment of the configuration of thelight-transmitting elements 18 of the panel 10 of the present inventionis shown in FIG. 8. In that configuration, the light-transmittingelements, identified as sheets 32, are formed planar films oflight-transmitting material positioned in a grid pattern through thethickness of the panel 10 and retained in position by the primarybuilding material 16. The sheets 32 may be uniformly spaced from oneanother by the primary building material 16 and crossed, as shown, orthey may be staggered in alternative or randomized patterns, dependentupon the light-transmitting characteristic of interest. The space of thepanel 10 between the interior side 12 and the exterior side 14 notoccupied by the sheets 32 is occupied by the primary building material16. Additionally, one or more of the individual light-transmittingsheets 32 may be formed of uniform thickness from the exterior side 14to the interior side 12 of the panel 10. Alternatively, the sheets 32may be of varied thickness, with the sheet thickness substantiallyuniform through the primary building material 16, but having either orboth ends thereof at the exterior side 14 and/or the interior side 12 ofgreater thickness. This alternative thickness arrangement allows forgreater light-receiving or light-producing capability where the lightenters or exits the sheets 32, but without increasing the overall volumeof the light-transmitting elements within the primary building material16. As a result, this particular arrangement aids in maintaining thestructural and/or insulative characteristics of the panel 10 whileenhancing light transmission. The sheets 32 may be used in combinationwith the light-concentrating elements 20 shaped as represented in FIG.5.

A third embodiment of the configuration of the light-transmittingelements 18 of the panel 10 of the present invention is shown in FIGS. 9and 10. In that configuration the light-transmitting elements 18, extendthrough the primary building material 16 from the interior side 12 tothe exterior side 14. However, rather than straight-line individualfibers or flat panels as shown in FIGS. 6-8, the light-transmittingelements 18 are arched or curved in cross-section as shown in FIG. 9.The extent of the curvature of each light-transmitting element 18 isdependent upon the desire to facilitate or block light transmissionthrough the panel 10. The curvature may be simple or compound.

As an example, if there is an interest to aid in warming a buildingusing the panel 10 during winter months and to minimizesunlight-generating heat during summer months, the light-transmittingelements 18 may be arranged as shown in FIG. 9 with respect to the sun'spassage through the sky as represented in FIG. 11. This arrangementwould focus and transmit more sunlight when the sun is low on thehorizon (winter months) while focusing and transmitting less light whenthe sun is high (summer months). In general, the light-transmittingelements 18 may be arranged in the primary building material 16 and inrelation to the light-concentrating elements 20 to maximize or minimizelight transmission through the panel 10 as desired by conforming withthe arch of the sun when and where desired. The light-transmittingelements 18 may be formed as individual shaped fibers or continuoussheet with a repeating arch-shaped curve throughout the sheet.

The embodiment of the present invention shown in FIG. 9 also shows thearray of light-concentrating elements 20 in a close-packed arrangement.This arrangement may be preferably for the light-transmitting element 18orientation shown in any of the figures. The close packing of thelight-concentrating elements 20 minimizes dead spaces, which dead spacesreduce the ability to take maximum advantage of capturing lighttransmitted by the sun. The space between individual lens is packed withprimary building material 16 which is essentially insulative material.That insulative material does not aid in concentrating light to thelight-transmitting elements 18. Nevertheless, a trade-off may be madebetween transmission effectiveness and fabrication goals.

Any of the three alternative arrangements of the light-transmittingsheets 32 as shown in FIGS. 7-10 may have certain advantages over use ofthe light-transmitting fibers 30 of FIG. 6. Specifically, it may beeasier, and therefore less expensive, to fabricate the sheets 32 ratherthan the fibers 30. Additionally, the sheets 32 enable the individualviewing the interior side 12 of the panel 10 to observe the transmittedimage from multiple angles within the building. That is, unlike lightemission from a point, light emission from a plane (the sheets 32)allows for an image to shift when viewed from multiple angledobservances of the plane. Use of the sheets 32 in a grid pattern asshown in FIG. 8 increases the number of angles from which the panel 10may be viewed and the observable representation of the image on theother side of the panel 10 maintained. Of course, the sheets 32 take upa greater portion of the overall volume of the panel 10 than do acorresponding number of fibers 30, such as, for example, when a likenumber of like-sized lenses are used as the light-concentrating elements20. Further, as noted, the optional use of light-transmitting withcurved arches 19 of the light-transmitting elements 18 of FIGS. 9 and 10allows for the formation of panels that transmit light during selectedtimes of the day and year to provide building heating during only thewinter months, for example, or lighting at only specific times of theday.

The panel 10 of the present invention in the several embodiments shownand in other related embodiments may be fabricated in a variety of waysto produce the several arrangements and configurations oflight-transmitting elements 18 as described herein. The panel 10 may befabricated using a thermoplastic material to form the light-transmittingelements 18. The thermoplastic material may be extruded through a die orset of dies to create an array of cylinders, strands or fibers. Theformed light-transmitting elements 18 may then be attached as an arrayof desired configuration to the inner wall of the component functioningas the exterior side 14 of the panel 10 to be formed. The primarybuilding material 16 is then applied to the same inner wall of theexterior side 14 in a manner that substantially or completely fills thegaps between individual ones of the light-transmitting elements 18. Theprimary building material 16 may be any material suitable for fillingthe gap and performing as an insulative or structural material. Forexample, the filling material may be a foamable polymer. Thelight-concentrating elements 20 may then be applied to the outer wall ofthe exterior side 14 of the panel. The light-concentrating elements 20may be molded in place on the exterior wall or they may be preformed andbonded to the exterior wall. For example, the material used to producethe light-concentrating elements 20 may be a polymer material capable ofbeing injection molded or thermoform molded in situ. Generally stated,the panel 10 may include extruded light-transmitting elements 18 spacedfrom one another by a filler material as the primary building material16, and injection-molded polymeric light-concentrating elements 20.

In regard to the panel 10 including one or more fibers 30 as representedin FIG. 6, there are several fabrication options. In a first fiber-basedpanel fabrication option, strands of optical fiber held on a spool maybe pushed or pulled through a fluid, which fluid may be processed into asolid, such as an insulative foam solid that is represented as theprimary building material 16. For example, the liquid may bepolyurethane curable into a foamed solid. The fibers are positioned inthe uncured fluid where desired prior to the curing step. Strands offibers may be repeatedly positioned within the fluid to build up a gridwith an appearance such as that shown in FIG. 6. The fluid may be curedafter the fiber strands have been positioned where desired. Theresultant foam/fiber strands composition may be cut or otherwise formedinto panels of building material having a light-transmittingcharacteristic. The light-concentrating elements 20 may then be added toa side of the fabricated panel defined as the exterior side 14 in aconcentrator adding process described herein. It is to be noted that thefiber strands may be extruded and positioned in the fluid rather thanpulled or pushed from a spool. It is also to be noted that the fluidmaterial may be more structural than insulative, such as a concretefluid allowed to cure with the fiber strands in position where desired.

In a second fiber-based panel fabrication option, the fluid may beallowed to cure or otherwise harden but having channels establishedtherein for subsequent placement of the light-transmitting elements 1.8.The fiber strands may then be drawn into the channels so formed.Alternatively, the channels may be filled with a liquid that will cureinto an optical material, such as an optical epoxy. The cured opticalepoxy has light-transmitting characteristics suitable for the intendedpurpose. In this fabrication option, the material used to. form theprimary building material 16 may be poured or injected into a moldcavity of selectable dimensions and having surfaces treated with arelease material. The mold cavity includes an array of pins extendingthrough the thickness of the cavity and arrayed in a pattern ofselectable configuration. The poured or injected material is allowed tocure, foam or otherwise harden and the resultant solid with channels inthe shape of the pin array is removed. Alternatively, the primarybuilding material 16 can be extruded with the air channels left open.The optical material is then inserted into the formed channels. Thisfabrication method enables use of relatively sophisticated fiber arraygeometries. Additionally, the light-concentrating elements 20 may beformed as part of the process, based on inserts placed in the mold. Forexample, the light-concentrating elements 20 may be formed as Winstoncones. Further, this method of fabrication allows for fabrication of thelight-transmitting elements 18 and the light-concentrating elements 20at the same time, rather than fabrication of the panel and subsequentattachment of the light-concentrating elements 20 thereto.

In a third fiber-based panel fabrication option, the fibers and thestructural material would be formed at the same time in a coextrusionprocess. That is, the material used to form the primary buildingmaterial 16 would be forced in or through a mold or die along with thematerial forming the fiber strands oriented in a desired configuration.The coextruded composition is cut to desired thickness to produceindividual panels in a continuous process. Optionally, a third materialmay be extruded to provide an interface with a low refractive indexbetween the optical material of the light-transmitting elements 18 andthe primary building material 16. This extrusion method may be wellsuited for high-volume automated manufacturing.

The fabrication of the fiber-based panels may require more complexoperations than the fabrication of the sheet-based panel represented inFIG. 7. One method for fabricating the sheet-based panel involvesunrolling optical film from a roll into a sheet of selectabledimensions. The sheet is coated or otherwise treated with the fluidmaterial, which is then allowed to cure into solid form with the sheetadjacent thereto. The sheet and material may be positioned within aretainer, such as a trough or mold, with dimensions approximating thedesired cross-sectional dimensions of the finished panel. The process ofplacing sheets and the fluid may be repeated until a satisfactorybuildup of the composition is completed. Alternatively, the sheets andstructural material may be coextruded in a manner similar to thatdescribed above for the third fiber-based panel fabrication option. Inanother alternative, the sheet of optical film and the primary buildingmaterial 16 may be preformed sheets of appropriate thicknesses that arealternately stacked and then bonded to a preformed light concentratingarray on one surface perpendicular to the stack, such as a lenticulararray, and an optical film or sheet on the other side. The primarybuilding material 16 may be a nonmetallic material such as a foamableurethane or a concrete. The finished lay up may form a single panel ormay be cut into multiple panels. The light-concentrating elements 20 maythen be applied to a selected surface of the formed panel.

The grid pattern of the sheet-based panel represented in FIG. 8 may befabricated in a manner as described in the first fiber-based panelfabrication option, but with fibers of optical material replaced withthe primary building material 16 coated in a liquid that will cure intothe optically transparent grid pattern when sections of the primarybuilding material 16 are placed together. Alternatively, the primarybuilding material 16 and the light-transmitting elements 18 may becoextruded in an intersecting pattern. Alternatively, thelight-transmitting elements 18 may alone be extruded and then theresultant grid can be filled with the primary building material 1 6mwhich may be an insulative powder.

The light-transmitting elements 18 as curved light guides represented inFIGS. 9 and 10 may be fabricated by coextrusion. They may also beextruded, molded or thermoformed, for example, and then spaced withsheets of the primary building material 16 or coated with a liquid thatwill cure to form the primary building material 16 with thelight-transmitting elements 18 therein. The light-transmitting elements18, may also be formed as a grid with fabrication methods as mentionedabove.

As noted, the light-concentrating elements 20 provide an advantage ofthe present invention in maximizing light transmission while minimizingadverse effects on the structural or insulation characteristics of thepanel 10. For that reason, it is desirable that they be applied to theexterior side 14 and configured in a way that focuses incoming light tothe light-transmitting elements 18 as effectively as possible. Anygeometry that funnels light from a larger area into a smaller area wouldbe more useful than no funneling at all. However, favorable geometriesinclude, but are not limited to, spherical, aspheric, and Winston cone,at least for the fiber-based panel. That is, geometries that focus thelight to a point or reduced cross sectional area. For the film-basedpanel configuration, preferable geometries include, but are not limitedto, ones that produce elongated ray patterns, such that they focus thelight in a line rather than to a point. For the grid-based panelconfiguration, preferable geometries include, but are not limited to,ones that produce elongated ray patterns in two axes, conformingsubstantially to the pattern of the grid of light-transmitting elements.An example would be given by two lenticular arrays super-imposed uponeach other at 90 degree angles. It should also be noted that thelight-concentrating elements 20 may have a flat geometry and yet stillact as light concentrators of the present in that they may have agradient in their refractive indices such as is found in GRIN lenses.

The light-concentrating elements 20 may be produced in sheet form andformed directly on the exterior side 14 of the panel 10. Prior toapplying the light-concentrating elements 20 to the exterior side 14,the light-concentrating elements 20 may be fabricated using existinglens array manufacturing techniques including, but not limited to,molding, extruding and embossing. The array of light-concentratingelements 20 may be formed directly on the exterior side 14, preferablyby first preparing that surface of the panel 10 to ensure suitablebonding of the array to the panel 10. That bonding may be achieved byforming the array on the exterior side 14 or by adhering a preformedarray to the exterior side 14. Alternatively, as described above, thearray may be formed when forming the light-transmitting elements 18.That is, the light-transmitting elements 18 and the light-concentratingelements 20 are fabricated at the same time such that they are alignedand have the same fabrication characteristics. That may be done insteadof fabricating each separately and then attaching the array aligned sothat individual ones of the light-concentrating elements 20 are properlyaligned with corresponding ones of the light-transmitting elements 18.

In another method of fabrication, the primary building material 16 isfirst formed, including with spaced channels where thelight-transmitting elements 18 are to be positioned, as previouslydescribed. This method permits establishment of the positioning of thelight-transmitting elements 18 and the desired shape of the array oflight-concentrating elements 20, such as in the form of Winston cones.Material used to create the light-transmitting elements 18 and thelight-concentrating elements 20, such as a curable fluid with opticalproperties when cured, is then directed into the established channelswithin the preformed primary building material 16 phase of the compositepanel 10. A mold including cavities in the desired shape of the array isfilled and then the fluid allowed to cure and solidify in the desiredshape. The mold is then removed.

In another example of a method of fabricating the light-concentratingelements 20 to the exterior side 14, a curable fluid with opticalcharacteristics when cured may be applied in fluid form to the exteriorside 14 of the previously formed primary building material 16. The fluidmay be a UV-curing ink or adhesive formulated to produce an opticalpolymer, preferably with a high refractive index. Light of anappropriate wavelength, dependent upon the fluid selected, may then bedirected from the interior side 12 through either channels establishedin the primary building material 16, or through light-transmittingelements 18 within such channels, to the curable fluid residing on theexterior side 14. The light is preferably transmitting at one or moreselected and controlled angles so that the fluid cures on the exteriorside 14 in the desired shapes of lenses to establish the array oflight-concentrating elements 20. The light is transmitted for acontrolled period of time so that curing of the fluid stops when theindividual lenses are of the desired size and shape. Any excess fluid onthe surface of the exterior side 14 that is not the subject of lightcuring is then removed and the cured material remaining forms the lensarray. Additional light curing may be done as then needed. The advantageof this method of fabrication is that the individual light-concentratingelements 20 are automatically aligned with respective ones of thelight-transmitting elements 18.

The light-transmitting elements 18 and the light-concentrating elements20 may be fabricated of any material that is transmissive of light inthe visible and/or infrared range. The same material may be used forboth, or different materials may be used. The light-concentratingelements 20 may be applied to either or both of the interior side 12 andthe exterior side 14 of the panel 10. The material selected may be glassor polymeric. Suitable polymeric materials include, but are not limitedto, thermoplastics such as polymethylmethacrylate, polycarbonate,polyvinyl chloride, polyvinyl dichloride, polyvinyl difluoride,polystyrene, polypropylene, and polyester; thermosets such asoptical-grade polyurethanes, epoxies, and acrylics. Materials that aretransmissive in the wavelength range of about 8-14 μm may be useful forthe light-transmitting elements 18 and/or light-concentrating elements20 when the light-concentrating elements 20 are located on the interiorside 12 of the panel 10. For example, that arrangement may be of usewhen the intent of the panel 10 is to transmit radiant heat out of abuilding to cool it.

The choice of material as the primary building material 16 of the panel10 is relatively broad. The choice is dependent upon the particularstructural and/or insulative characteristics desired for the panel 10.In one application, for which the panel 10 is to be primarily aninsulative component of a building, the primary building material 16 maybe selected from, but not limited to, foam, glass fiber, polymermicrofibers, perlite, and aerogel; provided the material selected doesnot remove significant light from the light-transmitting elements 18,through absorption or transmission, for example. In another application,for which the panel 10 is to be primarily a structural component of abuilding, the structural material 16 may be selected from, but notlimited to, wood, concrete, and aluminum or other metallic material,provided the material selected does not remove significant light fromthe light-transmitting elements 18. Further, the primary buildingmaterial 16 may be, or may be joined thermally to, a material thatfunctions as a storage mass. That is, the panel 10 or an array of thepanels 10 may be used to transmit light that produces heat which isconducted to the storage mass material. When the panel 10 no longer aidsin generating heat in the building, the storage mass material mayproduce heat for the building. In this application of the invention, thepanel 10 aids in supplying a heat sink.

In further consideration of the material selected as the primarybuilding material 16, it is useful to evaluate the Refractive Index (RI)of the material. The RI of the material has an effect on thelight-transmitting capability of the panel 10 when there is no airinterface between the materials. Standard insulation materials do nottransmit light without significant loss and scattering. If the primarybuilding material 16 of the panel 10 is in direct physical contact withthe light-transmitting elements 18, and the structural material 16 has aRI equal to or greater than that of the material of thelight-transmitting elements 18, the majority of light desired to betransmitted through those elements will be scattered and/or absorbed bythe primary building material 16. However, a material selected as theprimary building material 16 having a RI lower than that of the materialof the light-transmitting elements 18, then the light passing throughthe light-transmitting elements 18 will be reflected back and scatteringand/or absorption by that phase of the panel 10 will not occur. Thoseskilled in the art will recognize that the greater the difference in RIbetween the selected material of the structural material 16 and thematerial of the light-transmitting elements 18, the greater the numberof angles of light transmission will result. When the RI differential isunderstood, the particular geometry of the array of light-concentratingelements 20 may be established to focus light to the light-transmittingelements 18 at angles that will result in light transmission rather thanscattering or absorption. Those skilled in the art will recognize thatany number of array geometries may be created to work well with theparticular materials selected for the structural material 16 and thelight-transmitting elements 18.

Optical fibers may be treated or modified to increase the RIdifferential between the light-transmitting elements 18 and the primarybuilding material 16. For example, a glass fiber or an acrylic fiber maybe coated with a fluorine-containing polymer, such as polyvinyldifluoride (RI=1.42). Alternatively, air with a RI=1, or polyvinylacetate with a RI=1.47, may be adjacent to the fiber, or sheet for thepanel construction of FIGS. 7-10. Examples of air in contact with thelight-transmitting elements 18 include the use of glass or polymer fiberinsulation, a packing material such as perlite or aerogel, or foamdelaminated or otherwise unattached to the surface of thelight-transmitting elements 18, to give an effective RI value that isthat of air. In addition, materials such as polyvinyl acetate orpolyvinyl difluoride may be foamed adjacent to the light-transmittingelements 18 to make direct contact therewith, or the unfoamed versionsmay be coated as a thin coating on the outside of the light-transmittingelements 18, such as during a coextrusion fabrication process. When acoating or other treatment with relatively low RI value is directlycontacted to the exterior surfaces of the light-transmitting elements18, the primary building material 16 may be selected without regard toits particular RI value. That is, the selected coating, rather than theselected primary building material 16, causes the light reflection.

As expected for the function of the panel 10 of the present invention,there will be exposure to external elements, including sunlight itself,which may cause degradation of the materials chosen to fabricate it. Forthat reason, the materials may be treated to minimize ultravioletdegradation and oxidation. There exist standard commercially availableantioxidants, such as hindered phenols, and UV absorbers, such asmodified benzophenones that are available and can be added to thematerials of construction. Similarly, additives and/or coatings may beemployed in the formation of either or both of the light-concentratingelements 20 and the primary building material 16 to block UV lightand/or infrared light to allow light transmission while avoidingtransmission of damaging UV wavelengths and heating infrared wavelengthswhere lighting but not heating of the building is desired.

The panel 10 of the present invention may be used to save energy withina building by effectively drawing in the heat associated with sunlightwithout compromising insulative characteristics. The insulativeproperties of the panel 10 may be improved by increasing its thicknesswhile still enabling light transmission through the light-transmittingelements 18. The use of the light-concentrating elements 20 increasesthe percentage of light transmitted across the panel 10 with minimalreduction in physical properties of the primary building material 16. Inthe configuration of the panel shown in FIG. 3, light passes mainly inone direction, from exterior to interior, so that individuals can seeout of the building but others cannot see into the building. Further,the panel 10 of the present invention may be used any time there is aninterest in bringing light across a thermal barrier. For example, it maybe used as an improvement to a Trombe wall. It may be used to improvethe characteristics of a conventional wall, such as by providing abetter heat source as indicated herein. For example, the panel 10 may beaffixed to a conventional wall structure, such as a concrete wall. Thesun's light would pass through the panel 10 and heat the concrete. Theconcrete, in turn, may then be a thermal source for the building, andwould retain heat without overheating the building. As air is exchangedwithin the building, the thermal mass of the concrete wall would heatthat air. This arrangement may supplement or replace existing internalheating systems, dependent upon the amount of sunlight available. Theuse of a panel that selectively transmits light during the heatingseason while rejecting light during the warmer months of the year wouldbe extremely useful for this application. The panel 10 of FIGS. 9-10would be suitable for this purpose. A panel 10 of the present inventioncould also be used for solar hot water heating with the benefit ofbringing the light into the insulated envelope of the building such thatwater can be directly heated without the need for antifreeze solutionsand heat exchangers. Still further, one or more of the panels 10 may beconfigured with an external appearance recognized as a conventionalbuilding exterior appearance. To aid this appearance, the lightconcentrating sheet can be painted any color on its inner surfacewherever the light-transmitting element 18 is not attached or theprimary building material 16 can be colored any desired color.

The present invention is an apparatus to improve lighting and/or energyusage characteristics of a building. The present invention is also amethod of fabricating the structure with such characteristics. While thepresent invention has been described with particular reference tocertain embodiments of the panel 10, including the primary buildingmaterial 16, the light-transmitting elements 18 and thelight-concentrating elements 20, it is to be understood that it includesall reasonable equivalents thereof as defined by the following appendedclaims.

1. A light transmitting building panel comprising: a. a first surfaceand a second surface, the first surface including thereon one or morelight-concentrating elements arranged to concentrate light striking thefirst surface; b. one or more light-transmitting elements arranged toreceive concentrated light from the one or more light-concentratingelements, wherein each of the one or more light-concentrating elementsextends from the first surface to the second surface; and c. a primarybuilding material extending between the first surface and the secondsurface, wherein the primary building material spaces individual ones ofthe one or more light-transmitting elements from one another, andwherein the primary building material does not transmit light as well asthe one or more light-transmitting elements.
 2. The light transmittingbuilding panel as claimed in claim 1 wherein the light-concentratingelements are arranged as an array of lenses.
 3. The light transmittingbuilding panel as claimed in claim 1 wherein the light-transmittingelements are optical fibers.
 4. The light transmitting building panel asclaimed in claim 3 wherein the optical fibers have a cross section thatis not round.
 5. The light transmitting building panel as claimed inclaim 1 wherein the light transmitting-elements are sheets of opticalmaterial.
 6. The light transmitting building panel as claimed in claim 1wherein the light-transmitting elements form an extended grid of opticalmaterial.
 7. The light transmitting building panel as claimed in claim 1wherein the primary building material is a thermal insulator.
 8. Thelight transmitting building panel as claimed in claim 7 wherein theprimary building material is a foam insulation.
 9. The lighttransmitting building panel as claimed in claim 7 wherein the primarybuilding material is an insulative powder wherein the insulative powderis retained in the panel between the first surface and the secondsurface, and wherein the second surface is formed of a lighttransmitting material.
 10. The light transmitting building panel asclaimed in claim 1 wherein the primary building material is a loadbearing material.
 11. A method for fabricating a light-transmittingpanel having structural and/or insulative characteristics, the panelincluding a material used to form a primary building material withlight-transmitting elements extending therethrough andlight-concentrating elements on at least one surface thereof, the methodcomprising the steps of: a. injecting the material used to form theprimary building material into a mold cavity of selectable dimensionsand including an array of pins extending through the thickness of thecavity and arrayed in a pattern of selectable configuration of thelight-transmitting elements; b. curing the material with channels in theshape of the pin array to form a panel; c. removing the array of pinsfrom the channels; d. inserting a fluid having optical characteristicsinto the channels; e. curing the fluid to form the light-transmittingelements; and f. applying the light-concentrating elements to a surfaceof the panel
 12. The method as claimed in claim 11 wherein the channelsare in the form of individual ports.
 13. A method for fabricating alight-transmitting panel having structural and/or insulativecharacteristics, the panel including a material used to form a primarybuilding material with light-transmitting elements extendingtherethrough and light-concentrating elements on at least one surfacethereof, the surfaces of the panel including an inner wall and an outerwall, the method comprising the steps of: a. extruding a plurality ofthe light-transmitting elements in a grid array, b. cutting the extrudedlight-transmitting element array to form a panel, c. affixed to theinner wall of the one surface of the panel; d. applying the materialused to form the primary building material to fill the spaces within thelight-transmitting element array; and e. affixing a molded array of thelight-concentrating elements to the outer wall of the surface of thepanel.
 14. The method as claimed in claim 13 wherein thelight-concentrating elements are formed by polymer injection molding.15. The method as claimed in claim 13 wherein the material used to formthe primary building material is a foamable polymer insulative material.16. The method as claimed in claim 13 wherein steps c and e arereversed.